다양한 이온선택성 투과막에서의 나노전기수력학적 현상에 대한 실험적 검증

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2020. 8. 김성재.Perm-selective media has been widely used in various applications such as desalination, electro dialysis and battery, etc. In addition, micro-/nano-electrokinetic phenomena near the permselective media have been intensively studied. In many studies, material or geometry of the perm-selective media were adjusted for the easy fabrication or the new physics. In this thesis, material of the permselective media was adjusted by using ionic hydrogel and bio-based material, and also geometry of Nafion membrane was adjusted to have an undulation shaped surface. So the thesis was divided into two parts, one is the adjusting material, and the other is the adjusting geometry. In Chapter 2, ionic hydrogel was introduced for capillarity ion concentration polarization (CICP). To overcome a world-wide water shortage problem, numerous desalination methods were developed with state-of-the-art power efficiency. However, a natural plant, mangrove can survive in salty environment with optimal power sources. As motivated by the desalting function of mangrove, here we proposed a spontaneous desalting mechanism, CICP. An ion depletion zone was spontaneously formed near a nanoporous material by the perm-selective ion transportation driven by the capillarity of the material, in contrast to an electrokinetic ion concentration polarization which achieves the same ion depletion zone by an external dc bias. This CICP device was shown to be capable of reduced an ambient flourecent signal more than 90% without any external electrical power sources. These results indicated that the CICP system can offer unique and economical approaches for a power-free water purification system. In Chapter 3, biodegradable materials originated from well-known organisms such as human nail plate were rigorously investigated as a role of permselective nanoporous membrane. Most of nanofabrication methods are sophisticated and expensive due to the requirement of high class cleanroom facilities, while low-cost and biocompatible materials have been already introduced in the microfluidic platforms. Thus, an off-the-shelf and biodegradable material for those nanostructures can complete the concept of an eco-friendly micro/nanofluidic platform. A simple micro/nanofluidic device integrated with such materials was fabricated. Distinctive evidences (visualization of ion concentration polarization phenomenon, ohmic/limiting/overlimiting current behavior and surface charge-governed conductance) would fulfill the requirements of functional nanostructures for the nanofluidic applications. Therefore, this bio-based material, nail plate, would be utilized as a one of key elements of the biodegradable and eco-friendly micro/nanofluidic applications. In chapter 4, micro/nano fluidic platform involving undulated surfaced Nafion membrane was investigated for the study of electrokinetic effect depending on the characteristic length scale of the system. Although the several studies have shown that overlimiting current was enhanced due to undulation surface at the long characteristic length (~O(100) mm), there are few studies that have shown undulation effect at the short characteristic length (~O(10) mm). In this chapter, we compared the undulation effect at two characteristic length of 15 mm and 150 mm. I-V characteristics were obtained at both 15mm and 150 mm and investigated the possibility of suppressing the undulation effect according to the depth of the device. In this thesis, experimental investigation of the nanoelectrokinetic phenomena through novel perm-selective media was introduced. In chapter 2, 3, material of perm-selective media was adjusted by ionic hydrogel or bio-based materials and in chapter 4, geometry of the conventional perm-selective media, nafion, was modified to reveal the new physics.이온선택성막은 해수담수화나 전기투석, 배터리등의 어플리케이션에 아주 광범위하게 활용되고 있다. 또한 이론적으로는 이온선택성 막 주변에서 일어나는 마이크로/나노 전기수력학적인 현상들에 대한 많은 보고가 있었다. 특히 이온선택성 막의 특성을 변경하는 것은 새로운 물리적 현상을 보여주거나 쉬운 공정법을 제시한다는 점에 있어서 많은 연구가 이루어 지고 있는데, 크게 이온선택성 막의 내부 구조를 바꾸거나 외부 모양을 바꾸는 두가지로 나누어 볼 수 있다. 본 연구에서는 이온수화젤이나 생체유래물질을 이용하여 내부 구조를 바꾸었을 때 와 나피온막의 표면을 파상형으로 제작하여 외부 구조를 바꾸었을 때 발생하는 현상에 대해 나타내었다. 따라서 본 연구는 두 파트로 나뉘는데 하나는 내부 구조를 바꾼 것이고 하나는 외부 모양을 바꾼 것이다. 두번째 장에서는 이온수화젤이 모세관이온농도분극현상을 발생시키는 이온선택성 막으로써 제시되었다. 전세계적인 물부족 현상을 해결하기 위해 다양한 해수담수화 방법과 효율증대를 위한 연구들이 진행되어 왔다. 하지만 맹그로브와 같은 식물은 극대화된 효율을 활용하여 염수환경에서 살아남는다. 이러한 맹그로브의 담수화 기능에 영감을 받아 모세관 이온농도 분극현상이 자발적인 담수화 메커니즘으로써 제시 되었다. 일반적인 전기동역학적인 이온농도 분극현상이 외부 전기장에 의해 구동되는 것과 달리, 수화젤 본연의 모세관 힘에의해 선택적 이온 수송을 만들어내면서 수화젤 주변에서 자발적으로 이온 농도 분극 현상이 발생한다. 이 모세관 이온농도분극현상은 이온의 표지로써 넣어준 형광물질을 외부 전기장없이 90%이상 줄어들게 하였다. 이러한 결과들은 모세관 이온농도분극현상이 외부 전원 없는 정수 시스템 시장에 도움이 될 것으로 기대된다. 세번째 장에서는 손톱과 같은 잘 알려진 생체 물질을 이용한 생분해성의 물질이 이온선택성 투과막으로써 제시되었다. 이온선택성 투과막을 만들기위한 대부분의 나노 공정은 복잡하거나 높은 수준의 청정단계를 필요로 하는 비싼 공정이다. 반면에 마이크로 유체 플랫폼에서는 이미 싸고 생체적합한 다양한 물질들이 이미 다양하게 연구되어 오고 있다. 따라서 생분해성의 이온선택성 투과막을 활용하면 친환경적인 마이크로/나노 유체 플랫폼의 개념을 완성시킬 수 있다. 간단한 마이크로/나노 장치가 제작되었고, 이온농도분극현상의 시각화, 옴영역, 한계영역, 과한계영역으로 대표되는 전류전압특성 그리고 포면전하 기반의 전도도등을 간단한 실험을 통해 밝혀냈다. 따라서 손톱과 같은 생체유래물질을 사용하면 환경친화적이면서도 생분해성인 마이크로 나노 장치에 적용할 수 있을거라 기대할 수 있다. 네번째 장에서는 파상형구조의 표면을 갖는 나피온 막이 포함된 마이크로/나노 유체 플랫폼이 제작되고 연구되었다. 특히 특성길이에 따른 전기동역학적인 효과들에 대해서 알아보았는데, 일반적인 파상형 구조의 표면을 갖는 연구들은 대부분 긴 특성길이 (~O(100) m)에서 실험되고 해석 되어 온 반면, 본 연구에서는 짧은 특성길이 (~O(10) m)에서의 효과 역시 실험하고 비교되었다. 특히 전류 전압 특성을 통해 파상형 구조의 효과가 짧은 특성길이에서 억제되는지를 살펴보았다. 본 연구에서는 이온선택성 투과막의 외부 모양이나 내부 구조를 변형하여 발생하는 새로운 현상이나 새로운 특징들에 대해 실험하고 보고 하였다. 두번째와 세번째 장에서는 새로운 내부구조를 활용한 이온선택성 투과막에 대해 연구하였고, 네번째 장에서는 외부 모양을 바꾸었을 때 일어나는 새로운 물리적 특징들에 대해 연구하였다. 본 논문을 통해 다양한 이온선택성 투과막에 대한 이해가 높아지고 더 다양한 연구들이 화발히 진행되기를 바란다.Abstract i Contents iii List of Figures vi List of Tables ix Chapter 1. Introduction 1 1.1. Permselectivity of the nanoporus membrane 1 1.2. Examples of permselective structures 7 1.2.1. Ion exchange membrane 7 1.2.2. Nafion 8 1.2.3. Synthetic hydrogel 9 1.2.4. Lithographically defined nanochannels 10 1.2.5. Others 11 1.3. Ion concentration polarization 12 Chapter 2. Ionic Hydrogel Membrane for Capillarity based Ion Concentration Polarization 14 2.1. Introduction 14 2.2. Materials and methods 17 2.2.1. Synthetic hydrogel as a perm selective membrane 17 2.2.2. CICP device fabrication 18 2.2.3. Experimental setup 21 2.2.4. Concentration measurement from reference fluorescent signal 22 2.3. Results and discussion 24 2.3.1. Imbibition rate through the ionic hydrogel 24 2.3.2. The measurement of hydrogel swelling 28 2.3.3. The formation of an ion depletion zone by CICP phenomenon 30 2.3.4. The restoration phase by a diminished imbibition 34 2.3.5. Experimental analysis for the behavior of fluorescent dye 36 2.3.6. Asymmetric formation of the ion depletio zone in the cente-connection device 41 2.4. Conclusions 43 Chapter 3. Bio-based Membranes for Nanofluidic Applications 44 3.1. Introduction 44 3.2. Nail plate as a perm-selective membrane 46 3.3. Materials and methods 48 3.3.1. Nail device fabrication 48 3.3.2. Experimental setup 52 3.4. Results and discussion 53 3.4.1. The formation of ion depletion zone upon nail device 53 3.4.2. The I-V characteristics of the nail device 55 3.4.3. The conductance profile of the nail plate 56 3.5. Conclusions 59 Chapter 4. Undulated Nafion Membrane for Investigation of Electroconvective Instability 60 4.1. Introduction 60 4.2. Materials and methods 64 4.2.1. Undulation device fabrication 64 4.2.2. Experimental setup 67 4.3. Results and discussions 69 4.3.1. Visualization of vortices of Duckhins mode 69 4.3.2. I-V characteristics of the undulation device 71 4.4. Conclusions 72 Appendix 73 A. Analytical and numerical solution of the CICP 73 B. Hen egg yolk and albumen as a bio-based perm-selective membrane 88 Bibliography 99 Abstract in Korean 104Docto

Rapid Prototyping of Microfluidic Devices:Realization of Magnetic Micropumps, Fuel Cells and Protein Preconcentrators

With the growing importance of miniaturized energy applications and the development of micro Total Analysis Systems (μTAS), we have realized microfluidic devices, namely, magnetic micropumps, microfluidic fuel cells and membrane-based protein preconcentrators, all having high application potential in future. The choice of rapid prototyping microfabrication technologies and the selection of affordable materials are important aspects, when thinking of commercialization. Thus, we have employed powder blasting, polymer molding and assembly technologies during devices fabrication throughout the thesis. The first type of microfluidic device that we present is a poly(methyl methacrylate) (PMMA) ball-valve micropump with two different designs of the electromagnetic actuator, as optimized by the finite element method. The integration of a permanent magnet in a flexible polydimethylsiloxane (PDMS) membrane, which is clamped into PMMA structure, is proposed for providing a large stroke of the pumping membrane, making the micropump bubble-tolerant and self-priming Focusing on low power consumption for μTAS integration, another type of magnetic micropump with active valves is realized. It consists of a microfluidic chamber structure in glass that is assembled with a PDMS sheet, which comprises two valving membranes and a central actuation membrane, having each an integrated permanent magnet that is peristaltically actuated by a rotating arc-shaped permanent magnets assembly. A lumped circuit model is developed to predict and describe the frequency-dependent flow rate behavior for this type of pump. Powder blasting and PDMS molding rapid prototyping technologies are employed for realization of these two types of micropumps. Fuel cells with fluid delivery and removal options, having chemical reaction sites and electrode structures that can be realized in a microfluidic format, have high potential for applications. Therefore, microfluidic direct methanol fuel cells with embedded ion- permselective medium are studied and such type of fuel cell is realized by integrating a narrow Nafion strip in a molded elastomeric structure. A mechanical clamping assembly technology enables leakage-free operation and stable performance. The characterization reveals its output power density, using H2O2-based oxidant, is among the high-performance direct methanol fuel cells in microscale. Re-using the technology of the fuel cell chip, with its particular ion-permselective Nafion membrane and assembly method, we also have developed a protein preconcentrator with high purification performance. Our device can preconcentrate negatively charged biomolecules located at the anodic compartment side of the Nafion strip within only a few minutes with a high preconcentration factor. Moreover, a complex microfluidic finite element model is proposed to study and understand the physics of the preconcentration effect. Finally, we conclude the thesis with an outlook on future developments based on our work of the project and on the assembly technologies for microfluidic device integration

MEMBRANE-INTEGRATED AND MEMBRANE-FREE MICRO AND NANOFLUIDICS FOR ACCURATE MOLECULAR TRANSPORT IN BIOLOGICAL ASSAYS

Department of Mechanical EngineeringNanofluidics has a comparable characteristic length to the size of ions and biomolecules, so that it can be used as an efficient platform to conduct accurate biochemical assays/analyses. In particular, the nanofluidic elements are often embedded into microfluidics, forming integrated micro/nanofluidic networks for even more complex and systematic applications such as electrokinetic pumps, transistors, and energy convertors. Such innovative applications using unique mass-transport phenomena in micro/nanofluidic devices become available with the development of novel and precise nanofabrication techniques. For example, conventional nanolithography techniques such as electron or focused-ion beam lithography are used widely because of high degree of precision and accuracy of patterning. Another general nanofabrication method is micro-electromechanical system (MEMS)-based techniques that include both top-down (e.g., silicon etching) and bottom-up (e.g., thin-film deposition) approaches. However, it has been a challenge to fabricate the mixed-scale micro/nanofluidic devices by using either the conventional nanolithography utilizing the high-energy beams or the conventional MEMS-based nanofabrication because of the cost, time, throughput, and incompatibility issues of the methods. In particular, the limitations become more critical when both the microfabrication and the nanofabrication techniques need to be used in series to make micro/nano multi-scale structures. Therefore, an innovative alternate technique is specifically required to address the current weaknesses of both the conventional nanolithography and the MEMS-based nanofabrications. This dissertation describes novel and unconventional methods to fabricate mixed-scale micro/nanofluidic devices by integrating nanoporous hydrogels and ion selective membranes (ISMs) into microfluidic devices (membrane-integrated micro/nanofluidics). On the other hand, the micro/nanofluidic devices can be also fabricated by employing microfabricated ratchet structures that perform the same functions of a membrane, and by intentionally creating nanoscale cracks to produce nanochannels (membrane-free micro/nanofluidics). The dissertation???s early chapters deal with the development of novel nanomaterial-integrating methods to accurately control mass-transport phenomena at the micro/nanofluidic interfaces. A variety of hydrogel membranes are employed to enable pure diffusive or pure electrophoretic transport for accurate and active controls of chemical environments. In addition, ISMs are used to perform permselective ion transport for electrokinetic applications. The late chapters of this dissertation introduce membrane-free mixed-scale micro/nanofluidic devices that possess enhanced capabilities compared to the membrane-based devices, including higher precision and robustness in mass-transport controls, and higher compatibility with existing microfluidic components. First, an arrowhead-shaped ratchet microstructure in a microfluidic device physically compartmentalizes micron-sized bacterial cells but allows diffusion-controlled chemical environments without convective drag to the cells, which is commonly performed by a nanoporous membrane or a nanochannel. That is, the microfabricated ratchet structure acts the same function of a nanofluidic element without nanofabrication. Second, nanochannels and microchannels are fabricated simultaneously by an unprecedented cracking-assisted nanofabrication technique (called crack-photolithography) that relies only on a standard photolithography process. The crack-photolithography produces well-controlled micro/nanochannels in any desired shapes and in a variety of geometric dimensions, over large areas and with a high-throughput. Hence, mixed-scale micro/nanofluidic devices can be fabricated by the same technique that is used to fabricate a microchannel without additional nanofabrication processes and expensive equipment. Basically, the membrane-integrated and membrane-free micro/nanofluidic devices in this dissertation have the same mission, the transport control of biomolecules and chemical species to conduct biological assays in an accurate and high-throughput manner. As practical applications, the mixed-scale micro/nanofluidic devices are used for performing electrokinetic biosample pretreatments such as concentration and separation for ultra-sensitive and ultra-selective detection of target analytes such as proteins, particles and bacterial cells. In addition to the electrokinetic biomolecular/bacterial handling, the devices are also used for accurate characterizations of bacterial behavior such as chemotaxis and gene expression under convection-free and diffusion-controlled chemical stimulations. The role of a nanofluidic element such as a nanoporous membrane and a nanochannel array in microfluidics is essential to enable accurate and permselective transports of ions and molecules in various bioassays. In this context, the proposed membrane-based or membrane-free micro/nanofluidic devices play both microfluidic and nanofluidic functions without complicated nanofabrications, resulting in time-/cost-efficient and high-throughput fabrication. Thus, the research achievements in this dissertation substantially contribute to popularize and revolutionize the micro/nanofluidic systems and technologies, which have been hindered due to expensive and time-consuming conventional nanofabrications.ope

Micro/Nano-Chip Electrokinetics

Micro/nanofluidic chips have found increasing applications in the analysis of chemical and biological samples over the past two decades. Electrokinetics has become the method of choice in these micro/nano-chips for transporting, manipulating and sensing ions, (bio)molecules, fluids and (bio)particles, etc., due to the high maneuverability, scalability, sensitivity, and integrability. The involved phenomena, which cover electroosmosis, electrophoresis, dielectrophoresis, electrohydrodynamics, electrothermal flow, diffusioosmosis, diffusiophoresis, streaming potential, current, etc., arise from either the inherent or the induced surface charge on the solid-liquid interface under DC and/or AC electric fields. To review the state-of-the-art of micro/nanochip electrokinetics, we welcome, in this Special Issue of Micromachines, all original research or review articles on the fundamentals and applications of the variety of electrokinetic phenomena in both microfluidic and nanofluidic devices

Fast Detection of Low-Abundance Proteins Based on Ion Concentration Polarization

Molecular detection and analysis are of fundamental importance in disease prevention, disease diagnosis, medical treatment, drug delivery, food industry, and environmental monitoring. Conventional immunoassays require hours of incubation for low concentration analytes (femtomolar) since the rate-limiting step is the transport of target molecules to the biosensors. Thus, a new technology for fast and sensitive immunoassay is highly desirable for disease monitoring and personalized treatments. The work reported in this thesis is focused on developing silicon microfabrication technologies for sensors that can detect low concentration proteins (femtomolar) in a short time (tens of minutes). We first demonstrate the use of germanium (Ge) films as sacrificial layers that allow the patterning of proteins onto surfaces with commonly used organic solvents. As researchers miniaturize biosensors and microfluidic devices down to submicron scales, high-resolution biomolecule conjugation compatible with these processes is highly desirable. The presented technique is scalable to high volume manufacturing and is compatible with nano- and microfabrication processes, including standard lithography. We achieved nanoscale resolution and misalignment with this technique. We then discuss the development of ICP-based preconcentration devices on silica and silicon substrates. We report two nanofabrication strategies in this chapter that enhance the accumulation of protein molecules via 1) an increase in the number of nanochannels per microchannel and 2) an increase in the depth of nanochannels. Increasing the depth of nanochannels leads to the switch from silica substrates to silicon substrates, using deep reactive ion etch (DRIE). We also report the attempts for antibody immobilization in the ICP preconcentrators using previously reported Ge technique. However, due to the instability of antibodies in the drying process, we switched to bead-based immunoassays in our preconcentration devices. After the demonstration of protein preconcentration in our devices, we present a scalable method for fabricating hundreds of vertical nanochannels (6.5 µm deep) employing ion concentration polarization (ICP) enrichment for fast analyte detection. Compared to horizontal nanochannels, massively paralleled vertical nanochannels not only provide comparable electrokinetic functions but also significantly reduce effective fluid resistance in each microfluidic channel, which enables microbead loading for sensing purposes. These nanochannels filter microbeads by size and preconcentrate analytes at the anodic side of the test area via electrokinetic entrapment. The device is capable of enriching protein molecules by >1000 fold in 10 min. We demonstrate fast detection of IL6 down to 7.4 pg/ml with only a 10 min enrichment period followed by a 5 min incubation, which is a 162-fold enhancement in sensitivity compared to that without enrichment. Our results demonstrate the possibility of using silicon/silica-based vertical nanochannels to mimic the function of polymer membranes for protein enrichment

Développement d’un laboratoire sur puce pour la préconcentration sur support monolithique. Application à l'enrichissement et la séparation en ligne de phosphopeptides.

A lab on-a-chip is a miniaturized device that integrates onto a single chip different analytical steps (preconcentration, separation, detection...) with minimal sample consumption and short analysis time. They are potentially beneficial in phosphorylated biomarker analysis for which a preconcentration step is necessary because of their low abundance in biological fluids. That's why selective enrichment methods of phosphopeptides have been developed in recent years in particular those based on solid supports like Immobilized Metal Affinity Chromatography (IMAC). Among the solid supports, organic polymer monoliths present practical advantages when used in microchips due to their ease of preparation and in situ polymerization. The aim of this work was to develop a lab-on-a-chip integrating a monolithic support for online IMAC-based preconcentration and electrophoretic separation of phosphopeptides.In the first part, we developed two innovative approaches which allowed us to synthesize, for the first time, an ethylene glycol methacrylate phosphate-co-bisacrylamide (poly (EGMP-co-BAA)) monolith by a photo-driven process in microsystems. The first monolith synthesis approach was developed in glass microchannels using an inverted epifluorescence microscope as UV-irradiation source. The second approach was based on the photochemical properties of a new initiator which allowed the simultaneous synthesis and anchorage of the monolith in native polydimethylsiloxane (PDMS) microchips. A characterization (morphology, permeability, porosity and specific surface area) of (poly (EGMP-co-BAA)) monolith was then performed which demonstrated the potential of this monolith for preconcentration.Then a glass microchip electrophoresis method coupled to a detection by fluorescence was developed to separate a mixture of phosphopeptides fluorescent models differing with the position and number of phosphorylation sites. The phosphopeptides were detected in less than 2 min with excellent resolution (R> 3) and good efficiencies ranging from 11000 to 25000 plates. Finally, an integrated microdevice was developed by combining online preconcentration based on IMAC-Zr4+ and separation/detection of phosphopeptides. The performance of this integrated microdevice to capture and to elute the phosphopeptides was demonstrated and signal enhancement factors (SEF) higher than 340 were obtained. This lab-on-a-chip device opens news perspectives for phosphoproteomic applications and the diagnostic of diseases where the pathophysiological process involves phosphopeptidesLes laboratoires sur puce sont des dispositifs miniaturisés qui offrent la possibilité d'intégrer en ligne toutes les étapes de la chaîne analytique tout en réduisant les volumes d’échantillon et les temps d’analyse. Ainsi, ils constituent potentiellement un outil de diagnostic particulièrement adapté pour l’analyse de biomarqueurs phosphorylés, pour lesquels une préconcentration est nécessaire en raison de leur faible abondance dans les fluides biologiques. C’est pourquoi, de nouvelles méthodes, dédiées à l'enrichissement de phosphopeptides, ont été développées ces dernières années et en particulier celles utilisant des supports solides basées sur la chromatographie d’affinité sur des ions métalliques immobilisés (IMAC). Parmi les supports solides intégrables en microsystème, les monolithes organiques constituent une option privilégiée grâce à la possibilité d’être synthétisés in situ. Le but de ce travail de thèse était donc de développer un laboratoire sur puce intégrant une préconcentration des phosphopeptides sur support monolithique basé sur le principe de l’IMAC et leur séparation électrophorétique en ligne.Dans un premier temps, nous avons développé deux approches innovantes qui ont permis de synthétiser pour la première fois un monolithe à base d’éthylène glycol méthacrylate phosphate (EGMP) et de bisacrylamide (BAA) par voie photochimique dans des microsystèmes. La première stratégie développée dans des puces en verre repose sur la synthèse du monolithe à l’aide d’un microscope à épifluorescence. La deuxième approche est basée sur les propriétés photochimiques d’un nouvel amorceur qui a permis de synthétiser et d’ancrer le monolithe, en une seule étape, aux parois des puces en polydiméthylsiloxane (PDMS). Une caractérisation de ce monolithe en termes de morphologie, de perméabilité, de porosité et de surface spécifique a ensuite été réalisée. Ceci a permis de démontrer le potentiel de ce monolithe pour la préconcentration.Dans un deuxième temps, une méthode de séparation par électrophorèse couplée à une détection par fluorescence a été développée sur puce en verre. Celle-ci a permis de séparer un mélange de phosphopeptides modèles fluorescents possédant différents sites et degrés de phosphorylation. Les phosphopeptides ont été détectés en moins de 2 min avec une excellente résolution (R>3) et une bonne efficacité (plateaux théoriques compris entre 11000 et 25000). Enfin, le couplage en ligne du module de préconcentration monolithique et de séparation/détection a été réalisé. Sur ce dispositif miniaturisé, une préconcentration basée sur l’IMAC-Zr4+ a ainsi été développée. L’efficacité de la capture et de l’élution des phosphopeptides a été démontrée et des facteurs de préconcentration supérieurs à 340 ont été obtenus. En conclusion, ce laboratoire sur puce ouvre des perspectives très prometteuses dans le domaine du diagnostic de pathologies dont le processus physiopathologique implique des phosphopeptides.Mots clés : laboratoire sur puce, microsystème, phosphopeptide, IMAC, monolithe, photopolymérisation, préconcentration, électrophorèse sur puc

SURFACE ENABLED LAB-ON-A-CHIP (LOC) DEVICE FOR PROTEIN DETECTION AND SEPARATION

Sensitive and selective chemical/biological detection/analysis for proteins is essential for applications such as disease diagnosis, species phenotype identification, product quality control, and sample examination. Lab-on-a-chip (LOC) device provides advantages of fast analysis, reduced amount of sample requirements, and low cost, to magnificently facilitate protein detection research. Isoelectric focusing (IEF) is a strong and reliable electrophoretic technique capable of discerning proteins from complex mixtures based on the isoelectric point (pI) differences. It has experienced plenty of fruitful developments during previous decades which has given it the capability of performing with highly robust and reproducible analysis. This progress has made IEF devices an excellent tool for chemical/biological detection/analysis purposes. In recent years, the trends of simple instrument setting, rapid analysis, small sample requirement, and light labor intensity have inspired the LOC concept to be combined with IEF to evolve it into an “easily-handled chip with hours of analysis” from the earlier method of “working with big and heavy machines in a few days.” Although IEF is already a mature technique being applied, further LOC-IEF developments are still experiencing challenges related to its limitations such as miniaturizing the device scale without harming the resolving/discerning ability. With the facilitation of newly technologically advanced/improved fabrication tools, it is completely possible to address challenges and approach new limits of LOC-IEF. In this dissertation, a surface enabled printing technique, which can transfer liquid to a surface with prescribed patterns, was firstly introduced to IEF device fabrication. By employing surface enabled printing, a surface enabled IEF (sIEF) device running at a scale of 100 times smaller than those previously reported was designed and fabricated. Commercial carrier ampholytes (PharmalyteTM) with different pH range were engaged to generate a continuous pH gradient on sIEF device. Device design and optimized fabrication conditions were practically investigated; establishment of pH gradient was verified by fluorescent dyes; dependencies of electric field strength and carrier ampholytes concentration were systematically examined. To further optimize the sIEF system, dependencies of surface treatment and additive chemicals were explored. Fluorescent proteins and peptides were tested for the separation capability of sIEF. Finally, the well optimized sIEF system was used as a tool for real protein (hemoglobin variants and monoclonal antibody isoforms) separations. Hemoglobin variants test results revealed that sIEF is capable of separating amphoteric species with pI difference as small as 0.2. Monoclonal protein tests demonstrated the capability of sIEF to be a ready-to-use tool for protein structural change monitoring. In conclusion, this new sIEF approach has lower applied voltages, smaller sample requirements, a relatively quick fabrication process, and reusability, making it more attractive as a portable, user-friendly platform for qualitative protein detection and separation

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals